Orthogonal Frequency Division Multiplexing (OFDM) communication systems is a widely developed technique in the field of wireless digital communications thanks to the high possibilities offered by digital signal processing and Discrete Fourier Transform computations.
However, the efficiency of the process strongly depends on the estimation of the channel, which is achieved thanks to the communication of pilot signals within the subframe.
FIG. 1 illustrates the particular structure of the time-frequency OFDM grid, corresponding to a sub-frame, with the location of the pilots.
Many mechanisms are known in the art for computing an estimation of the channel vector hk (k corresponding to the discrete instant k), including iterative algorithms deriving the particular knowledge of hk from the knowledge of hk−1 and the new information brought be the pilots received at the instant k.
Generally speaking, the channel estimation is much more effective when one knows the law of variation of the channel—its time correlation—and when one may store the high volume of data derived from the received pilots so as to elaborate the most comprehensive knowledge of the channel estimation.
However, it is clear that the storage of a high volume of data increases the amount of storage required for the estimation process and moreover the amount of digital processing resources for processing such information.
For those reasons, many channel estimation processes are based on an iterative mechanism for computing the estimate ĥk of the vector channel only based on the preceding estimate ĥk−1 and the newly received information. Such iterative mechanisms show clear limitations particularly when the channel shows a large delay spread prohibiting accurate interpolation between the OFDM subcarriers.
In such an environment, but not exclusively, there is a need for an effective iterative mechanism, which takes advantage of all the information being available at a given instant k−1 for computing the estimated channel ĥk at the instant k.
Such is the technical problem to be solved by the present invention